To get more power [one shot body shots, not head or neck shots] and less noise from a gun [does not wake up the wife], I have found that I want to get the powder expansion ratio up and the muzzle pressure down.
The threshold of super sonic gas is one atmosphere above ambient.
What does it all mean?
Compressed small charges, long barrels, and large calibers.
What does THAT mean?
A big BB gun.
How about handguns?
Even a primer will be too much charge to be quiet with a handgun.